| Category | Key item | Short notes |
|---|---|---|
| Definition/Identifiers | Disease name | Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO); defined within the POLG-related ataxia-neuropathy spectrum (ANS) (pqac-00000008, pqac-00000013) |
| Definition/Identifiers | Synonym/relationship | ANS is an umbrella term that includes disorders previously referred to as MIRAS and SANDO (pqac-00000014, pqac-00000016) |
| Definition/Identifiers | Identifier status | OMIM for SANDO was not directly captured in readable evidence; MONDO/Orphanet/ICD/MeSH not captured in retrieved sources (pqac-00000014) |
| Etiology | Causal gene | POLG is the principal causal gene; it encodes mitochondrial DNA polymerase gamma required for mtDNA replication/repair (pqac-00000015, pqac-00000008) |
| Etiology | Inheritance | Biallelic pathogenic POLG variants are common in recessive POLG disease/SANDO-spectrum presentations; homozygous p.A467T and compound heterozygous cases are reported (pqac-00000010, pqac-00000012) |
| Etiology | Recurrent variants | A467T, W748S, and G848S are major recurrent POLG variants across POLG-related disease cohorts; p.A467T is repeatedly linked to SANDO cases (pqac-00000008, pqac-00000009) |
| Core phenotypes | Sensory ataxia/neuropathy | Ataxia is often early and dominant, frequently driven by proprioceptive loss from sensory neuropathy; absent sensory nerve action potentials and sensory axonal neuropathy are typical (pqac-00000002, pqac-00000010, pqac-00000001) |
| Core phenotypes | Dysarthria and ophthalmoparesis | Progressive dysarthria with ophthalmoparesis/ophthalmoplegia and ptosis form the classic clinical triad; gaze limitation is often bilateral and progressive (pqac-00000002, pqac-00000007, pqac-00000010) |
| Additional features | Other neurologic features | Dysphagia, exercise intolerance, seizures/epilepsy, hearing loss, myopathy, neuropathic pain, and encephalopathy may occur; PEO can appear late in some patients (pqac-00000002, pqac-00000016, pqac-00000001) |
| Diagnostics | Genetic testing | Final diagnosis relies on identification of deleterious POLG variants; sequencing of mtDNA-maintenance genes and broader mitochondrial testing is recommended in appropriate phenotypes (pqac-00000002, pqac-00000006, pqac-00000007) |
| Diagnostics | Electrophysiology and imaging | NCS/EMG commonly show sensory axonal neuropathy; EEG may show occipital slowing/epileptiform abnormalities in POLG disease; MRI can show cerebellar atrophy or thalamic/occipital/cerebellar lesions, though imaging may be noncontributory early (pqac-00000001, pqac-00000002, pqac-00000008) |
| Diagnostics | Muscle pathology/biochemistry | Muscle biopsy can show COX-deficient ragged-red fibers and multiple mtDNA deletions; however, biopsy may be normal and blood mtDNA can be less sensitive than muscle-derived material (pqac-00000010, pqac-00000009) |
| Pathophysiology | Molecular chain | POLG dysfunction impairs mtDNA replication/repair, causing mtDNA deletions and/or depletion, respiratory-chain/OXPHOS failure, reduced ATP production, and mitochondrial dysfunction in high-energy tissues (pqac-00000002, pqac-00000013, pqac-00000017) |
| Pathophysiology | Tissue-level consequences | Post-mitotic tissues such as muscle and nervous system accumulate mtDNA defects; biopsy evidence includes COX deficiency and ragged-red fibers, consistent with mitochondrial myopathic/neurodegenerative injury (pqac-00000010, pqac-00000013) |
| Natural history/outcomes | Onset and progression | Onset is variable from childhood to late adulthood; gait ataxia is a common initial symptom, and progression is chronic and degenerative with substantial morbidity (pqac-00000001, pqac-00000015) |
| Natural history/outcomes | Outcome signals | In broader POLG cohorts, epilepsy-associated disease can be severe: status epilepticus occurred in 46.4% of reviewed epilepsy cases and 5-year survival was 30.2%; childhood-onset POLG disease had only 6/40 survivors in one series (pqac-00000008, pqac-00000012) |
| Treatments/management | Supportive care and contraindications | No definitive disease-modifying standard therapy is established; management is multidisciplinary and symptomatic. Valproic acid/valproate is contraindicated in POLG mutation carriers because it can precipitate liver failure (pqac-00000014, pqac-00000007) |
| Recent research 2023-2024 | Nucleoside therapy trial | Phase 2 open-label POLG trial NCT04802707 tested enteral deoxycytidine/deoxythymidine (dC/dT); in the first 10 participants, mean NMDS improved 27.3→20.7, mean GDF-15 1031→729 pg/mL, EEG improved in 5/8 abnormal baselines, with diarrhea in 2 patients (pqac-00000015) |
| Recent research 2023-2024 | Preclinical fibroblast findings | In POLG1 fibroblasts, ATGC nucleoside supplementation increased mtDNA content and significantly improved mtDNA recovery after ddC-induced depletion in quiescent cells; lower-dose regimens reduced toxicity concerns (pqac-00000017) |
| Models | Experimental systems | Yeast (Saccharomyces cerevisiae; MIP1 ortholog), patient fibroblasts, and broader POLG disease models are used to study mtDNA maintenance defects and therapeutic screening; yeast-based drug-drop tests are highlighted for mitochondrial disease discovery pipelines (pqac-00000019, pqac-00000017) |


*Table: This table condenses the main disease-knowledge-base attributes for SANDO from retrieved evidence, including etiology, phenotype, mechanisms, diagnosis, management, and recent 2023-2024 therapeutic developments. It is useful as a structured reference for curating core facts and citations.*